Portable power requirements have driven the development of battery technology to achieve high energy density and good power performance. One area of development includes the manufacture of electrodes by co-extruding conductive materials onto a substrate. Two aspects of battery development involve optimizing material density and ion transport. High density means higher packing of material, which leads to higher energy storage. Less dense material results in more electrolyte filling the volume, which enables faster lithium ion transport in the electrolyte, in the case of a lithium ion battery.
The co-extrusion process has been discussed in several US patents and US patent applications. Examples of these types of battery electrodes are discussed in U.S. Pat. Nos. 7,765,949; 7,780,812; 7,922,471; and US Patent Publications 20070279839, 20120156364 and 20120153211. U.S. Pat. No. 7,765,949 discloses a device for extruding and dispensing materials on a substrate, the device has at least two channels for receiving materials and an exit port for extruding the materials onto the substrate. U.S. Pat. No. 7,780,812 discloses another such device having a planarized edge surface. U.S. Pat. No. 7,922,471 discloses another such device for extruding materials that have an equilibrium shape that does not settle after deposition onto the substrate. US Patent Publication 20070279839 discloses a co-extrusion technique employing a honeycomb structure. US Patent Publications 20120156364 and 20120153211 disclose a co-extrusion head that combines streams of two or more materials into an interdigitated structure on a substrate, where there are multiple stripes of the materials.
In addition to the development of co-extruded materials, development has begun in three dimensional architectures. These three dimensional architectures achieve improved battery performance by reconfiguring the electrode materials currently employed in uniform monolithic batteries. A variety of three dimensional structures have been achieved as shown in FIG. 1. One example 10 has interdigitated cylindrical cathodes and anodes. Another example 12 has interdigitated cathodes and anodes with rectangular cross-sections. Yet another example 14 shows an array of cylindrical anodes coated with the thin layer of ion-conducting electrolyte with the remaining free volume filled with the cathode material. A last example 16 shows what is referred to as an ‘aperiodic sponge’ architecture in which the solid network of the sponge serves as the charge insertion cathode, which is coated with an ultrathin layer of ion-conducting electrolyte, and the remaining free volume is filled with an interpenetrating, continuous anode.
These architectures do have improved performance but are difficult to manufacture. The realization of the improvements can only occur if someone can manufacture the structures in a cost-efficient manner.